基于ARM的矫顽磁力仪的研制

设计了一种基于ARM的全自动矫顽磁力检测仪.该仪器以S3C2410为处理器,采用12位精度的串行AD TLV2544进行数据采集.将嵌入式Web服务器移植到ARM上,具有在线数据传输和远程故障诊断功能.同时采用了数控恒流源和开关电源退磁技术.该仪器检测精度高,测试样品体积大,温度适应性强,是一款适用于磁性材料矫顽力快速、准确检测的工业自动化仪器.     

Effect of film thickness on magnetic properties of Cr/SmCo/Cr films

Cr/SmCo/Cr films with different SmCo thickness were deposited on glass substrates by magnetron sputtering,followed by an annealing process at 550 °C for 20 min.Experimental results showed that the SmCo film of 30 nm exhibited two-phase behavior in the demagnetization process,the obvious kink was observed near zero.For the SmCo film of 50 nm,the kink was invisible,and a single phase like behavior was obtained in the demagnetization process.The reversal behavior became consistent in the thicker films.Moreover,the coercivity reduced and the saturated magnetization increased obviously with the increasing thickness.X-ray diffraction results indicated that the average grain size of SmCo 5 in the thicker films were almost 30 nm,but the quantity of SmCo 5 grains increased with the increasing thickness,which enhanced the intergrain exchange coupling(IEC) of the SmCo 5 hard phases.The increase of IEC improved the magnetic properties of SmCo films with increasing thickness.     

超高矫顽力NdFeB磁体研究

为制备超高矫顽力的烧结钕铁硼磁体,设计了材料配方(PrNd)23.5Dy8.7FebalAl0.7Nb0.6Cu0.02B1.05,采用了先进的工艺技术,包括片铸、氢爆碎(HD)、高纯氮气流磨制粉、高取向度密封成型、冷等静压、高温高真空烧结等.实验结果表明,由该工艺制备的粉末平均粒度为 4.5μm;磁体晶粒细小均匀,富钕相弥散分布在Nd2Fe14B主相周围.磁体的剩余磁通密度为1.12T,内禀矫顽力达到2430.2kA/m,最大磁能积达到了246.0kJ/m.     

纳米硬磁晶粒间的交换耦合相互作用和有效各向异性

以纳米Nd2Fe14B永磁材料为例,研究了硬磁晶粒间交换耦合相互作用对磁体有效各向异性的影响。结果表明晶粒间交换耦合相互作用随晶粒尺寸的减小而增强,材料的有效各向异性常数Keff随晶粒尺寸的减小而逐渐下降,Keff随晶粒尺寸的变化与矫顽力的变化规律相似。纳米单相永磁材料有效各向异性的减小是矫顽力降低的主要原因,交换耦合系数口aex实际上是各向异性的减小量。为保证纳米Nd2Fe14B材料具有较高的各向异性和矫顽力,晶粒尺寸应不小于30nm。     

Effect of Ti cap layer thickness on microstructures and magnetic properties of Ti/Ni/Ti films

Nanogranular Ti(3 nm)/Ni(30 nm)/Ti(t nm )(t=1,3,5,7,10) films were prepared by facing magnetron sputtering from Ti and Ni onto glass substrates at room temperature.The structural and magnetic properties of films strongly depended on the Ti layer thickness.X-ray diffraction(XRD) patterns of all as-deposited films showed strong FCC Ni(111) peak.Vibrating sample magnetometer(VSM) measurements indicated that the perpendicular coercivity of the Ti(3 nm)/Ni(30 nm)/Ti(3 nm) film reached about 36 kA/m.With the increase of Co layer thickness,coercivity(Hc) first increased and then decreased.The grain size and magnetic clusters slightly increased and the value of roughness(Ra) was smallest at t=3 nm.     

Improvement of coercivity and corrosion resistance of Nd-Fe-B sintered magnets by doping aluminium nano-particles

Nd-Fe-B permanent magnets with a small amount of Al nano-particles doping were prepared by conventional sintered method. Effect of Al content on magnetic property, corrosion resistance and oxidation properties of the magnets were studied. Investigation showed that the coercivity rose gradually, while the remanence decreased simultaneously with increase of Al doping amount. Further investigation revealed that most Al element diffused into the main phase and some Al element diffused into the Nd-rich phase. The autoclave test results showed that the corrosion rate of the magnets decreased with Al content increasing. After oxidation, the maximum energy product losses of the magnets with 0.0 wt.% and 0.2 wt.% Al nano-particles doping were 6.13% and 3.99%, respectively. Therefore, Al nano-particles doping was a promising way to enhance the coercivity and corrosion resistance of sintered Nd-Fe-B magnet.     

Effect of niobium on thermal stability and impact toughness of Nd-Fe-B magnets with ultra-high intrinsic coercivity

The effects of Nb on the thermal stability and impact toughness of ultra-high intrinsic coercivity of Nd-Fe-B magnets were investigated.The results showed that the addition of Nb could improve the thermal stability,and obviously increased the impact toughness of sintered Nd-Fe-B magnets.The optimum thermal stability of sintered Nd-Fe-B magnets was obtained when the content of Nb was 1.0 at.%.The maximum impact toughness of sintered Nd-Fe-B magnets was obtained when the content of Nb was 1.5 at.%,but the magnetic properties of sintered Nd-Fe-B magnets drastically deteriorated when the content of Nb increased from 1.0 at.% to 1.5 at.%.The microstructure showed that overfull Nb addition made many ultra-fine grains get together,which led to the density of sintered Nd-Fe-B magnets decline and drastically deteriorated the magnetic properties of sintered Nd-Fe-B magnets.     

Sm2Co17型高温稀土永磁的微结构与磁性能

采用透射电子显微镜（TEM）、扫描电子显微镜（SEM）、磁力显微镜（MFM）和原位X射线衍射（XRD）等探讨Sm2Co17型稀土永磁材料的胞状结构、畴结构和相结构及其对磁性能的影响,制备使用温度为500℃的高温稀土永磁材料。结果表明,Sm（CoFe0.11Cu0.10Zr0.03）7.5具有很好的高温稳定性,500℃时的磁性能为：Br=0.708 T,Hci=646.7 kA/m,BHmax=85.4 kJ/m^3;其磁畴宽度远小于晶粒尺寸,但大于胞状结构的尺寸,使用温度较高的磁体具有较小的磁畴和胞状结构;当使用温度小于300℃时,Sm2Co17型磁体内存在的相结构为2：17R、2：17H和1：5相,矫顽力主要受1：5相的钉扎而产生;当300℃〈t〈tc^1：5时,部分1：5相转变成中间相并最终转变成2：7相,磁体的矫顽力将由1：5相钉扎和2：7相形核所控制;当t≥tc^1：5时,磁体的矫顽力将全部由非磁性1：5相和2：7相形核所控制。     

辊速及晶化工艺对(Nd, Pr)13Fe80Nb1B6快淬薄带组织和矫顽力的影响

用熔体快淬法制备(Nd,Pr)_(13)Fe_(80)Nb_1B_6快淬薄带并晶化处理,研究辊速和晶化条件对其组织和矫顽力的影响.结果表明,在10～20、25和35 m/s分别得到纳米晶、部分非晶和完全非晶薄带,且在18 m/s制备的薄带有较好的c轴各向异性.快淬态薄带的矫顽力随辊速(10～25 m/s)的增大而增加.非晶薄带晶化后由(Nd,Pr)_2Fe_(14)B相和富稀土相组成,且完全非晶薄带晶化后比部分非晶薄带晶化后的矫顽力要高,这是由于前者比后者具有更均匀的微结构造成的.非晶薄带晶化后矫顽力最大为1616 kA/m,高的矫顽力与添加Pr和Nb有关.     

Al与Mo复合添加对NdFeB磁体矫顽力的影响

本文采用晶间合金化工艺将合金元素Mo和Al直接引入烧结Nd-Fe-B磁体晶间区域,改变晶间区域的合金体系和显微组织,以达到提高磁体矫顽力的目的.实验结果表明Mo在低温时效过程中可抑制晶间富Nd相与主相之间的平衡转变,使晶界区域析出细小二次主相晶粒,使矫顽力提高.